Locking device for electrical plug and socket arrangement



Sept. 13, 1938. L, N, DAVIS' 2,129,914

LOCKING DEVICE FOR ELECTRICAL PLUG AND SOCKET ARRANGEMENT Filed Oct. 4, 1935 INVENTOR:

LEW/8 NEWELL. DAV/s,

Ar TORNE Patented Sept. 13, 1938 UNITED STATES 2,129,914 LOCKING DEVICE FOR ELECTDIEICAL PLUG AND SOCKET Lewis Newell Davis,

signor to Douglas Santa Monica, Calif ware ARRANGE NT Santa Monica, Calif., as-

Aircraft Company, Inc., a corporation of Dela- Application October 4, 1935, Serial Nth-13,532

.1 Claim.

The invention constituting the subject matter of this application is an electrical plug and socket connection having a unique locking device forming a part thereof.

In manufacturing plants, particularly large ones, it is common practice to provide electrical sockets at certain locations throughout the entire factory so that an electrically operated device may be plugged in at any desired point in the factory. This is particularly a fact in those factories where it is necessary to move the apparatus around to various points where the apparatus is to be used.

Where no means is provided for holding the plug in the socket it is a nuisance to have the connection inadvertently broken, since it interrupts the workmans work and loses considerable time.

It is an object of my invention to provide an electrical connection in which the parts are locked together so that they cannot be accidently sep'arated; in which the locking device takes the strain which is imposed upon the parts when there is a pull exerted on the cord tending to separate the parts of the plug; in which the plug portion or removable portion is resiliently held in place; and in which the removable part of the electrical connection is so designed that it may be used in connection with electrical sockets or other stationary parts of an electrical connection even though they are not designed for utilizing the locking feature of the invention;

and which is strong and durable, cheap in construction; easy to install, and easy and conven-.

lent to operate.

Other objects and advantages of my invention will be pointed out in thefollowing detailed description of my invention.

Referring to the drawing in which I have illustrated a form of my invention which has been found to be highly satisfactory in commercial use: Fig. 1 is a. vertical sectional view through a form of my invention and is taken along a line indicated by the arrows 22 of Fig. 2. Fig. 2 is a plan view partially in section of the device shown in Fig. 1.

Fig. 3 is a. perspective view showing the locking member of my invention and the manner in which it is mounted on the removable part of the electrical connection.

Fig. 4 is a fragmentary sectional view taken on the line H of Fig. 2.

In the form of my invention illustrated herein I provide an electrical connection including a socket element In and a plug element H. Ac-

cording to standard practice, the socket element I 0 is mounted in an outlet box l2 which maybe mounted in a wall, or floor, or ceiling, or as a portable unit ll. In the form of the invention illustrated the socket element i0 is provided with three openings l5 which are positioned immediately above contacts It as shown in Fig. 4, and the plug element II is provided with projecting contact fingers i1 which are adapted to extend through the openings I5 and engage the contacts l6. This is all in accordance with standard practice. The plug element ll consists of a body proper I 8 which is adapted to fitv against the outer face of the socket element II) when the parts are installed together in proper electrical operating relationship. Extending from the plug element II is a flexible conductor l9 which is shown to be broken, but which in accordance with usual practice is extended to a suitable electrically operated device which is supplied with energy when the electrical connection is fitted together as illustrated by full lines in Fig. 1. My invention provides a locking means or looking member 2i which is preferably in the form of a yoke as shown. The yoke 2| is provided with a nave or hub portion 22 having an-opening 23 through which the flexible conductor l9 extends.

The yoke 2| is likewise provided with extending means in the form of a pair of parallel arms 24 which are adapted to extend on opposite sides of the plug element i i, as shown in Fig. 1. The locking means- 2i is provided with connecting means for the purpose of connecting it to the which have enlargementsor heads 26 mounted on the lower end thereof, these heads being pro-v vided with upper tapered -or' conical faces 21. The outlet box I2 is provided with a front plate or cover plate 28 having an opening 29 which and this plate 281s provided with a pair of armated slots 30 which are curved around a point located on the axis of the plug element II. The ends of the slots 30 are enlarged as indicated at 3| and these enlarged portions are of suflicient diameter to permit the heads 26 to be extended therethrough. The remaining portions of the slots, however, are not of such a size and therefore the walls of the plate 28 defining the edges of the slots 30 will be engaged by the inclined or tapered faces 21 if an attempt is made to pull the locking member outwardly from the posiexposes the outer face of the socket element l0,

. ends 3|.

1 plane below the wall 28 larged ends 3|.

tions shown in Fig. '1 or at any time when the pins 25 are. extended through the slots 30 and the heads are not in alignment with the enlarged The ends of the slots 30 opposite the enlarged ends 3| are provided with countersinks M which may be done by pressing the metal upwardly, as shown. This is done for the purpose of providing receiving recesses in which the heads 26 may rest when the locking member is in a fully assembled or installed position. Placed between the plug element locking means 2| is a resilient pressure applying means for the purpose of resiliently retaining the plug in completely assembled position and for re turning it to such pulled partly from place. This resilient means is preferably provided in the form of a compression spring a, the lower end of which engages a clamp 35 which forms a part of the plug element H, and the upper end of which preferably engagesa shoulder 36 which is provided in the opening 23. In the form of my invention shown the compression spring 34a is provided with an extension 31 which is of relatively small diameter and flts closely to the outer surface of the flexible conductor is and acts as a means for preventing a caking of the flexible conductor which is desirable in order to prevent breakage.

An added feature of my invention is the provision of a pliable sheet which is in the form of a rubber sheet 39 placed between the upper end of the outlet box l2 and the cover 28 therefor. This is provided for the purpose of keeping dirt and other foreign matter from the outlet box i2 and its usefulness for this purpose is apparent from an examination of the drawing. Positioned in alignment with the openings l5 slits 40 are provided through which the contact fingers i1 may be extended.

In using the combination of my invention the first step in installing the parts together is to place the plug in installed position, as shown in full lines in Fig. 1. This may be done without engaging the locking member 2| and at this time the compression spring 34a holds the yoke 2| in a relatively raised position as indicated by the broken lines 43. The next step'in the installation is to engage the yoke 2| and to force it downwardly. This causes a compression of the spring against the plug element When the locking pins 25 approach the slots 30 the yoke is moved into an aligned position so that the heads 25 of the pins 25 will pass through the enlarged ends 8| of the slots 30. When the heads have passed through the enlarged ends 3| and rest in a the yoke is then rotated in a clockwise direction in the form of my invention illustrated and is rotated until the pins 25 reach the ends of the slots ill opposite the en- The yoke is then released and the force exerted by the spring 35:: in an upward direction raises the yoke and the pins attached thereto so that the tapered or inclined walls of the heads 26 rest in the countarsinks 34. This will be effective in holding the yoke 2| in the position illustrated in full lines in Fig. 1 and in re leasably locking the parts in this position.

It will be seen that when the parts are so installed the yoke 2| is attached directly to the n and'the I position if it is inadvertently cover of the outlet box i2, and that any forces or stresses of engagement of the yoke are transferred directly to the outlet box and not to the plug element or the conductor I9. It should, furthermore, be noted that by reason of the compression of the spring 34a between the yoke 2| and the plug element the plug element is resiliently retained in place. Should the flexible conductor Id be accidently pulled so that the plug element ii is slightly raised from place and is thereafter released, the spring 34a is preferably of suflicient strength to forthwith return the plug element to fully installed position. The parts are so designed that it is impossible to fully remove the plug element from place, it being noted that the space above the plug element II and below the hub 22 of the yoke 2| is insufflcient to allow a complete removal. Therefore, it is impossible to completely separate the plug element and the socket element, but when it is partially separated the spring 34a will, when the disturbing force is eliminated, return the parts to proper assembled,position.

The electrical connection. is disconnected by engaging the yoke, forcing it downwardly and then rotating it in a counter-clockwise direction, which brings the heads 26 into alignment with the enlargements 3| of the openings 30. The yoke is then allowed action of the spring 34a and thereafter the plug element may be pulled from place.

It will be seen that if the yoke 2| and spring 34a and associated parts constituting my invention are installed on a plug element, that the plug element may be used even though the locking device is not used. Therefore, the installing of my invention on any of the removable parts of an electrical connection will not prevent or interto be moved upwardly by the.

fere with its free'use on sockets or stationary which are not provided with cooperating Under such circumstances the parts attaching means.

.yoke 2| may remain in the position indicated by dotted lines 43.

I claim as my invention:

In a device of the class described the combination of a socket element having electrical contacts, guide openings therefor, and a' relatively flat wall having connection openings therein; a plug element having contact fingers adapted to extend through said guide openings and into engagement with said electrical contacts; a conductor connected to said plug element; a connecting yoke separate from said plug element having a hub in which there is an opening through which said conductor freely extends, arms extending at the sides of said plug element toward said socket element, and connection pins on said arms cooperating with said connection openings for locking said yoke to said socket element, said connecting yoke being separate from said plug element and surrounding said plug element when said connecting yoke is connected to said socket element and at that time constituting a protection means for said plug element; and a spring surrounding said conductor and compressed between said hub of said yoke and said plug element for resiliently holding said plug element in place.

' LEWIS NEWELL DAVIS. 

